1. Field of the Invention
This invention relates to a heat exchanger of the parallel flow type comprising a plurality of flat tubes and corrugated fins stacked alternately, a first header tank to which said tubes are connected by inserting one end thereof laterally into said first header tank and a second header tank to which said tubes are connected by inserting the other end thereof laterally into said second header tank.
2. Prior Art
Heat exchangers of the parallel flow type (e.g., vehicle-loaded condenser) conventionally comprise a plurality of flat tubes and corrugated fins stacked alternately, a first header tank to which said tubes are connected by inserting one end thereof laterally into said first header tank and a second header tank to which the tubes are connected by inserting the other end thereof laterally into said second header tank (each of said first and second header tanks usually comprises cylindrical pipe) so that parallel flows of refrigerant are established through a plurality of tubes between the first header tank and the second header tank.
Concerning the manner in which the respective tubes are connected to the respective header tanks, it is well known, as illustrated by FIG. 9, to form opposite ends of each tube 21 straight as viewed axially of the respective header tanks 22, then to insert this tube laterally into the respective header tanks 22 through respective insertion holes 23 with the straight formed ends extending beyond the edges of the insertion holes 23 by a predetermined extension to assure a sufficient brazing margin, and to braze these components together for integral connection therebetween (as disclosed, for example, by Japanese Patent Application Disclosure Gazettes Nos. 1986-235698 and 1988-112065). Such prior art employs the header tanks 22 each having a diameter larger than the width of each tube 21 so that the extent of the tube end extending into the respective header tanks 22 may be reduced and the refrigerant flow resistance occurring within the respective header tanks 22 may be alleviated.
However, such heat exchangers of the prior art inevitably encounters a problem that the use of large-diameter header tanks necessarily requires a correspondingly increased volume of refrigerant flowing therethrough although the refrigerant flow resistance can be certainly reduced by limiting the extent of the tube ends extending into the respective header tanks. It should be understood here that, so far as saving of refrigerant is concerned, small diameter header tanks are preferably employed in view of the fact that the volume of refrigerant normally occupying the header tanks corresponds substantially to 50% of that contained within the entire heat exchanger.
To solve this problem, it may be conceivable, as illustrated by FIGS. 10 and 11, to use small-diameter header tanks 24 to achieve the saving of refrigerant. However, such a countermeasure would necessarily result in a corresponding increase of the tube end extension into the respective header tanks 24 and, consequently, there would occur an undulant flow pattern of refrigerant around the tube ends, as indicated by a solid line arrow in FIG. 11, so the flow resistance and, therefore, the pressure loss would inconveniently increase.
This invention was made in view of the above-mentioned problem encountered by the conventional heat exchanger, to solve this problem in an effective manner.